I quit a heavy coffee habit recently.

I cut my caffeine in half each day (and went from a quarter cup to zero) I did experience some withdrawal symptoms, including headache, lethargy, and some mild but notable depression. The worst of it was over in a couple of days, I'd say the full deal took about a week and a half. Not a load of fun but honestly not that bad considering I was a heavy coffee drinker for 30 years.

I'd recommend drawing down a little slower than 50% a day. Maybe a third or quarter? Either way don't go cold turkey definitely draw down.